Talk:Planetary nebula

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Origin of name

There is a request to discuss the origin of the name planetary referring to this type of nebula. Herschel referred to '...the nebulae I have called Planetary...' in Phil. Trans, vol 79, p 225 (1789). The whole work can be read here: http://rstl.royalsocietypublishing.org/content/79/212.full.pdf+html.Robin Scagell (talk) 23:46, 20 April 2018 (UTC)

It is dubious because Antoine Darquier of Toulouse (1718-1802) used the term in January 1779 when he described the ring nebula in his notes "...a very dim but perfectly outlined; it is as large as Jupiter and resembles a fading planet." The usage is likely English bias against the French. Arianewiki1 (talk) 00:14, 8 June 2018 (UTC)

At 23:07 hours on the 28th of January your edit summary was: "Who really first coined the term 'planetary nebula still remains a matter of contention. What about Antoine Darquier de Pellepoix of Toulouse? Herschel only found they were gaseous. Origin is certainly French. Talkpage please". This is what about Antoine Darquier de Pellepoix of Toulouse: He has usually been credited with the discovery of the Ring Nebula in 1779. That is enough credit for him. He never claimed to have coined the phrase, planetary nebula, and no editor has given a quotation of him using the phrase. If the addition to the article were made claiming that Antoine Darquier de Pellepoix of Toulouse coined the phrase without a quote in support, that addition would need to be removed as original research. If there is no such quote of dear Antoine using the phrase, there is no point in further discussion, but that does not stop me from discussing. The English are notorious for stealing words from any language with which they come into contact. Far from being biased against the French, English speaking Americans are more prone to use innovations that are given Frenchy sounding names like french fries, french bread and champaign. So unless there is a quote to support that that astronomer from Toulouse used the phrase, planetary nebula or planetary nebulae in the plural, the current text in the article in this regard should be maintained the same. - Fartherred (talk) 01:13, 10 June 2018 (UTC)

"Herschel only found they were gaseous." Incorrect. He thought they were unresolved stars, actually. (Only NGC 1514 may have suggested otherwise.) As for "no editor has given a quotation of him using the phrase." There are many sources for this quote (three given). The problem is there is known to be some correspondence between Herschel and Darquier, with the discovered quote coming after Herschel, even though it was written before Herschel. The point is the round shapes of these nebulae looked similar in size to the planets, hence the name. It is far from WP:NOR. Also Messier found the Ring Nebula first not Darquier. Arianewiki1 (talk) 01:30, 12 June 2018 (UTC)

A citation supporting giving credit for coining the phrase is Hoskin, M. (2014) "William Herschel and the Planetary Nebulae". Journal for the History of Astronomy 45(2), pp. 209–225. which I do not know how to access and likely lack permission to access. This text from the article: "Herschel assigned these to Class IV of his catalogue of 'nebulae', eventually listing 78 'planetary nebulae'" is supported by p. 16 in Mullaney, James (2007). The Herschel Objects and How to Observe Them. Astronomers' Observing. It quotes Herschel using the phrase and applying the phrase to any thing that looked to him like a dim nebulous planet, including many galaxies. Herschel coined the term and later the use of it was refined to today's understanding of planetary nebulae.

Antoine Darquier de Pellepoix of Toulouse found the Ring Nebula independently after Messier found it and Antoine Darquier de Pellepoix of Toulouseand has usually been credited with the discovery of the Ring Nebula (exactly as I wrote above) in spite of his not finding it first. - Fartherred (talk) 02:19, 12 June 2018 (UTC)

• In 1785, Herschel said of the Ring nebula: "a nebula that has a concentric dark spot in the middle and is probably a ring of stars."
• As for this Darquier quote, a Google search confirms this as true. Jones "Messier's Nebulae and Star Clusters" pg.25, says this here. "...so it seems that Herschel might merely have adopted this description for the whole class." Evidence enough to support this claim.
• Messier found M57 on 31st January 1779, while Darquier said January 1779 (deduced as earlier). He found it while both he and Messier was both looking at (the same) passing comet. Arianewiki1 (talk) 02:49, 12 June 2018 (UTC)

Well, the Ring Nebula and who found which Messier object first is a side point. I hope you agree with the quote of Herschel using the phrase "planetary nebulae". - Fartherred (talk) 03:10, 12 June 2018 (UTC)

Herschel's invention and explanation of the term

In the opening section of the article, the mention of Darquier is interesting but not relevant. The prominence given to Darquier is misleading and the passage should be removed, or shortened and moved. Three sources are cited for the Darquier quotation; it is actually found in Messier's "Catalogue des Nébuleuses & des amas d'Étoiles" in the Connoissance des Temps (https://books.google.co.uk/books?id=-NnBsQU7QdgC&pg=PA259). Messier remarks on his entry number 57:

M. Messier a rapporté cet amas de lumiere sur la carte de la comète de 1779. M. Darquier, a Toulouse, découvrit cette nébuleuse, en observant la même comète, et il rapporte: “Nébuleuse entre gamma & beta de la Lyre; elle est fort terne, mais parfaitement terminée; elle est grosse comme Jupiter et ressemble à une planète qui s’éteindroit.”

There is no evidence that Darquier's remark (or Messier 57 itself) influenced the subsequent introduction of the term "planetary nebula" by William Herschel who explained the name in his paper, “On the Construction of the Heavens” [Phil. Trans., vol. lxxv., 1785, pp. 213-266.] At the time he believed that all nebulae consisted of unresolved stars, glowing in the manner of the Milky Way. He did not consider Messier 57 planetary; his prototypes for the class were NGC 7009 (the very first DSO he discovered, nicknamed the Saturn Nebula by Rosse in the 1840s) and NGC 7662 (nicknamed the “Blue Snowball” in the 1960s). Here are extracts from Herschel’s paper:

A Perforated Nebula, or Ring of Stars. Among the curiosities of the heavens should be placed a nebula, that has a regular, concentric, dark spot in the middle, and is probably a Ring of stars. It is of an oval shape... The light is of the resolvable kind, and in the northern side three very faint stars may be seen, as also one or two in the southern part... It is the 57th of the Connoissance des Temps. Fig. 5 is a representation of it.

Planetary Nebulae. I shall conclude this paper with an account of a few heavenly bodies, that from their singular appearance leave me almost in doubt where to class them. The first [NGC 7009, which Herschel discovered in 1782]... I have examined... with the powers of 71, 227, 278, 460, and 932; and it follows the laws of magnifying, so that its body is no illusion of light. It is a little oval, and in the 7-feet reflector pretty well defined, but not sharp on the edges. In the 20-feet, of 18.7 inch aperture, it is much better defined, and has much of a planetary appearance, being all over of an uniform brightness, in which it differs from nebulae: its light seems however to be of the starry nature, which suffers not nearly so much as the planetary disks are known to do, when much magnified. The second of these bodies [NGC 7662]... has a round, bright, pretty well defined planetary disk of about 12" diameter, and is a little elliptical... [Herschel then describes NGC 6369, NGC 6905, NGC 6984]. The planetary appearance of the two first [NGC 7009, NGC 7662] is so remarkable, that we can hardly suppose them to be nebulae; their light is so uniform, as well as vivid, the diameters so small and well defined, as to make it almost improbable they should belong to that species of bodies. On the other hand, the effect of different powers seems to be much against their light's being of a planetary nature, since it preserves its brightness nearly in the same manner as the stars do in similar trials. If we would suppose them to be single stars with large diameters we shall find it difficult to account for their not being brighter; unless we should admit that the intrinsic light of some stars may be very much inferior to that of the generality, which however can hardly be imagined to extend to such a degree. We might suspect them to be comets about their aphelion, if the brightness as well as magnitude of the diameters did not oppose this idea ; so that after all, we can hardly find any hypothesis so probable as that of their being Nebulae; but then they must consist of stars that are compressed and accumulated in the highest degree. If it were not perhaps too hazardous to pursue a former surmise of a renewal in what I figuratively called the Laboratories of the universe, the stars forming these extraordinary nebulae, by some decay or waste of nature, being no longer fit for their former purposes, and having their projectile forces, if any such they had, retarded in each others' atmosphere, may rush at last together, and either in succession, or by one general tremendous shock, unite into a new body. Perhaps the extraordinary and sudden blaze of a new star in Cassiopea's chair, in 1572, might possibly be of such a nature. But lest I should be led too far from the path of observation, to which I am resolved to limit myself, I shall only point out a considerable use that may be made of these curious bodies. If a little attention to them should prove that, having no annual parallax, they belong most probably to the class of nebulae, they may then be expected to keep their situation better than any one of the stars belonging to our system, on account of their being probably at a very great distance. Now to have a fixed point somewhere in the heavens, to which the motions of the rest may be referred, is certainly of considerable consequence in Astronomy; and both these bodies are bright and small enough to answer that end.

In 1790 he discovered NGC 1514 (a planetary nebula in the modern sense) and saw it as a "star with atmosphere". He then revised his theory, believing that some nebulae consisted of luminous fluid (possibly of planet-forming kind) rather than unresolved starlight. Many of the objects he classed as "planetary nebulae" (his Class IV) are really galaxies. — Preceding unsigned comment added by Andrew Crumey (talk • contribs)

Nope: Not true. Darquier, A. (1777) comments appear in his notebook, being Reference 3 in the article. This has been discussed several times on this Talkpage. It is evidence of perpetuated bias that has historically been mostly made by English writers. Sure Herschel tried to explain the phenomena of planetary nebulae, but the usage of the term predates this. Arianewiki1 (talk) 01:14, 20 March 2019 (UTC)

I have rewritten the discovery and terminology sections to bring out the facts. Duplication was removed and these sections were merged . Two new quotes and one new citation was added. We do not who coined the name 'planetary nebulae' but is expressed something that had been mentioned by more than one person. The text mentions both Darquier and Herschel in this context. ABZebra (talk) 14:24, 24 May 2021 (UTC)

Odd nomenclature

The planetary nebula known as PK 358-1.1, located at two degrees south of the galactic center, is also known as "BID" (so it is mentioned in THE DEEP SKY FIELD GUIDE TO URANOMETRIA 2000.0, chart 377). What is the meaning of "BID"? According to SIMBAD the BI must be Blanco, but... what is the "D"? Is it perhaps the fourth object (the D-object) in a catalogue from Blanco? DannyCaes (talk) 09:58, 22 January 2023 (UTC)

Peimbert type

For a B-type article, it should include a discussion of the 'Peimbert type' used to classify planetary nebulae. Praemonitus (talk) 23:00, 14 January 2025 (UTC)

Copy Edit of the whole article

brightly coloured planetary -> brightly colored planetary
Starting from the -> Starting in the 1990s
disk resembled a planet but -> disk resembled a planet, but
The origin of this term not -> The origin of this term is not
nebulous objects such -> nebulous objects, such
known) had spectra -> known), had spectra
Brightest of these was -> The brightest of these was
passes between -> pass between
in 1960s, -> in the 1960s,
eye in astronomic terms -> eye in astronomical terms
speeds gives rise -> speeds give rise The Other Karma (talk) 18:40, 17 October 2025 (UTC)

 Done Thank you for careful reading! Lova Falk (talk) 06:23, 21 October 2025 (UTC)

Gas or plasma?

The introductory sentence of the article currently states that a planetary nebula is a "glowing shell of ionized gas". Since the fluid has been ionized to a significant degree, the fluid stops being gas and starts being plasma, which is a distinct state of matter that has qualitatively different properties from gas.

One way to investigate whether a fluid is plasma is to look at the degree of ionization, which is where is the ion density and is the neutral particle density. Fig. 1 (top panel) of Sil et al. (2026) shows the number densities of different particles in a model of a planetary nebula as a function of distance from the star. Out to 0.022 pc, is pretty close to 100%, so the fluid is pretty close to a fully ionized plasma. Further out, it looks like maybe , and there's also a statement that n(e-)/n(Htot) ∼ 3.64e-2. In comparison, in the solar photosphere, which is a partially ionized plasma. Gzymqlxwj (talk) 02:44, 22 April 2026 (UTC)

@Gzymqlxwj, as I mentioned in my revert, I could not find a source referring to it as a plasma, while I could find several referring to it as a gas. If you want to change it, please at least provide a reliable source referring to it as a plasma. Even the source you link to as evidence for calling it a plasma says "The physical model parameters are listed in Table 1. Our standard model assumes a homogeneous spherical shell of gas surrounding a hot central star, a white dwarf, emitting as a black body"

Wikipedia is based on reliable sources, not on original research. Therefore, we should be consistent with the standard terminology in the astrophysics literature. All the literature I could find refers to it as a gas, not a plasma. Jcuhfehl (talk) 09:04, 22 April 2026 (UTC)

Oh that would have been easier than going through articles and trying to read numbers off of ionization profiles! Here's a NASA ADS search of refereed articles on planetary nebulae that use 'plasma' in the abstract and do not use 'gas' in the full text. Would something like this work?

Though often referred to as a gas by astronomers (Osterbrock & Ferland 2005), the fluid inside a planetary nebula has been ionized to a significant degree (Sil et al. 2026, page 3), and is in the plasma state of matter (Kulsrud 2004).

Also worth checking out are the first two sentences of the plasma article to see the definition of plasma, and the section on Plasma_(physics)#The_fourth_state_of_matter to make sure that things are consistent across articles. Gzymqlxwj (talk) 15:51, 22 April 2026 (UTC)

@Gzymqlxwj, firstly, I want to say that I believe that we do not disagree about the actual physics here; it is clear that the material in a planetary nebula is significantly ionized, and that plasma refers to a gas that is ionized. The disagreement here is what we should call it. My position is that we should use the term that is most often used in the literature. As the source you cite itself states "often referred to as a gas by astronomers", which shows that this is the common terminology. Also (note that I think it is not particularly strong evidence without actually reading the abstracts) the ADS query you used gives 26 results. If I flip it around (i.e. search for refereed articles that mention gas in their abstract but not plasma), I get 461 results, which is significantly more. Jcuhfehl (talk) 16:08, 22 April 2026 (UTC)

I do think that we are coming at this from different perspectives, which would be worth diving into. The question is whether plasma is a gas, or whether plasma is a distinct state of matter that is not gas. The usage "ionized gas" or "gas that is ionized" implies that plasma is a gas, rather than a fluid that has undergone a phase transition into a state of matter distinct from gas that behaves in qualitatively different ways.

Astronomers commonly define gas as: (1) gas, and (2) plasma. I'll call that gas (astronomer usage). Gas (astronomer usage) is ambiguous. Gas (astronomer usage) is also inconsistent with usage in plasma physics journals, like Physics of Plasmas, the Journal of Plasma Physics, and Plasma Physics and Controlled Fusion. Non-astronomers would think gas (astronomer usage) refers to gas (Wikipedia definition), which is misleading.

Regardless of whether plasma is used throughout the article, would there be consensus for me to add the sentence I proposed above without making any other changes? Or are there other edits to it that you'd suggest? The sentence purposefully sidesteps the question of whether plasma ∈ gas or plasma ∉ gas.

(By the way, thank you to everyone here for participating in this discussion — it shows that you really do care about science and making knowledge open to all!) Gzymqlxwj (talk) 17:32, 22 April 2026 (UTC)

I realized I misread your previous comment. I thought the "Though often ... state of matter" sentence was a quote from a book, but I misread it and it was a sentence you were proposing adding to the article. In principle, I think such a sentence would be appropriate, so long as the source you cite explicitly states that the envelope of a planetary nebula is in the gas phase (otherwise I think this would fall under WP:SYNTH). Unfortunately, I don't have access to the Kulsrud book so I cannot check this.

Also, out of interest, is the transition between a gas and plasma actually a phase transition (i.e. is there a discontinuity in one of the thermodynamic variables)? Naively I would expect the degree of ionization to increase continuously according to a Boltzmann distribution. If that is the case I would come down on the plasma is a subset of gas side, but I think that is mostly a semantic discussion which is indeed nicely avoided by the wording you proposed. Jcuhfehl (talk) 18:38, 22 April 2026 (UTC)

That is a wonderful question and I thank you for asking it! It is a phase transition, but it differs from other phase transitions because it is gradual rather than abrupt, as particles in a fluid gradually become ionized. The ionization is sometimes caused by heating up the fluid, but it can also be caused by photoionization (photons knocking electrons off of atoms/molecules like in planetary nebulae), applying a really strong electric field that pulls electrons off of atoms/molecules, or by having cosmic rays knock electrons off of atoms/molecules (like in molecular clouds). In practice, even a tiny ionization fraction is often enough for the fluid to engage in behavior that is qualitatively different from a completely neutral gas. The charged particles experience electromagnetic forces, but then they transfer momentum and energy to the neutrals via collisions, so the neutrals experience a drag force from the charged particles (often called ambipolar diffusion in astrophysics) and thus "feel" the magnetic field.

I'll wait a little longer on the proposed edit to give others a chance to respond, and for myself to double check the big pile of textbooks that I left in my office. 😅

Thank you again! Gzymqlxwj (talk) 19:47, 22 April 2026 (UTC)

I realized there is also another (very similar) possibility which might be acceptable for everyone. We could add a footnote right after calling it an ionized gas saying something like

While most astrophysicists refer to it as a gas, some use the term plasma instead [some source].

This sidesteps the problem of where in the article your sentence should be placed and avoids mentioning the fact that it is ionized twice (since that's already stated by saying ionized gas).

As a source to show that the term plasma is actually used by some, I found this one as an example, but I'm very open to any other reliable source instead as well. Jcuhfehl (talk) 06:03, 23 April 2026 (UTC)

@Gzymqlxwj, since we haven't gotten comments by other editors, would you find this solution acceptable? Jcuhfehl (talk) 16:35, 5 May 2026 (UTC)

How about a footnote like this?

In astrophysical literature, the term gas commonly refers to fluids in either of the gas or plasma states of matter.

A possible citation to add would be Schaffner et al. (2023), which is a position paper (kind of like a scientific editorial) submitted to the most recent heliophysics decadal survey in the US. (Disclosure: most of the authors are friends of mine.)

Thank you for following up on this! Gzymqlxwj (talk) 03:49, 6 May 2026 (UTC)

@Gzymqlxwj, I think the wording sounds good, but I disagree with the specific source you'd cite, since it does not mention planetary nebulae specifically. This is a difference between writing in a scientific journal vs on wikipedia, since here you are not allowed to synthesise different findings into a conclusion that is not explicitly stated. So to be able to draw the conclusion that planetary nebulae consist of plasma, we need a source that explicitly calls a planetary nebula a plasma, which is why I proposed the specific source that I did. (At least that is my understanding of the relevant policy WP:NOR) Jcuhfehl (talk) 07:01, 6 May 2026 (UTC)

Most sources describe planetary nebulae as being composed of ionised gas, which is certainly true. The distinction from plasma is arguable; some sources use the two terms interchangeably, others use plasma to refer only to particular situations of components of the gas where the distinction becomes important. So "ionised gas" covers it, but mentioning plasma somewhere seems like it could be helpful. There is one use of the word "plasma" in the article right now, and a reference that uses that term (or at least "low-density plasma") extensively. Other sources exist, but most are discussing very restricted definitions of plasmas. Lithopsian (talk) 15:50, 22 April 2026 (UTC)

Gas and plasma have qualitative differences in behavior; otherwise they wouldn't be considered different states of matter. Plasma has high electrical conductivity, while gas is an effective insulator. This may seem inconsequential, but this property can lead to behavior like coronal rain after a solar flare, where condensing plasma cools and falls back to the Sun along magnetic field lines. This behavior could not occur in a gas. Gzymqlxwj (talk) 16:09, 22 April 2026 (UTC)

As was mentioned on other talk pages, usage of the term plasma tends to get reserved for these cases where the plasma effects significantly influence the physics. In the example you give, the article mentions the fact that it is a plasma. However, (to my admittedly limited knowledge) these effects are not significant in planetary nebula, hence the reason why sources primarily refer to it as a gas. Jcuhfehl (talk) 16:19, 22 April 2026 (UTC)

The article does mention magnetic fields in a few places, and the second to last paragraph currently ends with: "Several have been shown to exhibit strong magnetic fields,[72] and their interactions with ionized gas could explain some planetary nebulae shapes.[56]" Gzymqlxwj (talk) 17:45, 22 April 2026 (UTC)

I agree with this, mentioning plasma somewhere in the full text of article could be a valuable addition. Jcuhfehl (talk) 16:14, 22 April 2026 (UTC)

Add section on magnetic field observations and effects?

In the gas or plasma discussion above, the topic of magnetic fields in came up. Would it be helpful to add a section that discusses the roles of magnetic fields in planetary nebulae? It would be something like Accretion disk#Magnetic fields and jets. Some of the discussion could go into astrophysical plasma. Possible questions to address include:

• How well are magnetic fields and their effects understood in planetary nebulae (PN)?
• How are magnetic fields observed in PN?
• What are typical magnetic field strengths and configurations?
• How does the magnetic pressure compare to the thermal pressure (i.e., what is plasma β)?
• How do magnetic fields affect the structure and evolution of PN?
• How are the magnetic fields generated?
• Is there any evidence for different plasma processes like magnetized shocks?
• How does PN eject interact with the interstellar magnetic field?
• What are typical ionization fractions in the material that has not been photoionized? (This affects how well coupled the neutral and charged particle components are, and is directly related to the section above.)

Thank you in advance to anyone working on this! Gzymqlxwj (talk) 18:32, 22 April 2026 (UTC)